1. Field of the Invention
This invention relates to devices useful for centering the cutting bit of an electric router regardless of the thickness of the material used. The present invention is particularly directed towards a centering fixture with height adjustable removable aligners which can be manufactured as the main base plate of an electric router or supplied as an auxiliary fasten-on base plate.
2. Description of the Prior Art
Electrically powered hand-held routers having a downwardly positioned cutting bit for cutting a grove in a wood surface edge are in common use in both woodworking shops and home hobby shops. A method of centering the cutting bit in relationship to the edge of the piece being grooved has been somewhat of a complicated procedure. Devices seen in past-art patents do not seem to adequately accomplish a simple alignment procedure and require a certain degree of expertise in the field to utilize the device.
Patents examined which appeared most pertinent were the following:
A patent issued to W. L. Mitchell on Feb. 7, 1961, U.S. Pat. No. 2,970,618 illustrates a "Guide Means for Hand Routers" which uses a tab along the edge of the piece being worked.
The patent issued to Groves on Apr. 15, 1980, U.S. Pat. No. 4,197,887, shows a router guide with adjustable guide posts which when very carefully spaced are adapted to engage the edge of the workpiece.
The electric drill attachment of Elsbrenner, U.S. Pat. No. 3,288,183, dated Nov. 29, 1966, and the Willis router of U.S. Pat. No. 3,289,718, data issued Dec. 6, 1966, both are illustrative of edge-mounted plates as centering guides.
The Fortune patent issued June 17, 1969, U.S. Pat. No. 3,450,001; the Zelik device, U.S. Pat. No. 3,478,788, dated Nov. 18, 1969; the Bailey router guide U.S. Pat. No. 3,509,923, dated May 5, 1970; and the multijob router guide kit in U.S. Pat. No. 3,635,268, dated Jan. 18, 1972, issued to Lange, are illustrative of various mechanical attachments offered as router guides.
Considered most pertinent to my invention is the Groves device of U.S. Pat. No. 4,197,887, issued Apr. 15, 1980. The radially adjustable guide posts shown in the patent are not readily accessible for adjustment once the plate is attached to the router. This type of radial adjustment can become loosened during use and can cause the router blade to vary from a centered position. My router base guide eliminates any need for radial adjustment by positioning the guides posts in extensions past the outer circumference of the plate surface in a diametric alignment. To center the router blade using my router guide on any width board, it is only necessary to turn the router until the guide posts contact the edges of the board. As is described in the following specification, the guide posts in my router guide are adjustable vertically and removable without detaching the guide plate from the router.
To my knowledge, the foregoing patents represented devices most pertinent to my invention. Although router alignment devices may necessarily be somewhat similar, my invention comprises a substantial improvement over those previously mentioned by not requiring manual adjustments to enable the device to be used for centering and by having guide post depth adjustments.